1. Field of the Invention
The present invention relates to a developing device that stores and supplies toner for forming a toner image, and to an image forming apparatus having the developing device.
2. Description of the Related Art
A developing device generally includes a developer storing section that holds a toner-containing developer and that transports the developer while stirring the latter, a developing roller that receives the toner from the developer storing section and carries the toner, and a developer regulating blade that regulates the amount of toner supplied to the developing roller. In the developing device having the above configuration, the friction heat generated due to developer stirring causes the temperature in the developing device to rise. This may induce toner melting in the developing device, which makes it difficult to achieve a toner image of good quality.
Techniques for suppressing temperature rises in developing devices are disclosed in, for example, Japanese Laid-open Patent Application No. 2004-109868. The developing device in Japanese Laid-open Patent Application No. 2004-109868 includes a ventilation duct disposed in the vicinity of a developer regulating blade. This configuration makes it possible that friction heat is dissipated by way of the developer regulating blade, which is in contact with the developer, to suppress temperature rises inside the developing device.
In the developing device, however, the developer adheres readily onto the surface of the developer regulating blade. This surface-covering developer may decrease the thermal conductivity of the developer regulating blade. The above-described suppressing effect on temperature rise is decreased, and hence it is difficult to realize toner images of good quality even when using the ventilation duct.
In the quest to improve image reproducibility, there is recently a growing demand for using smaller particle sizes in carriers and toner, which are the components of developers. The smaller particle size, however, makes the developer less fluid, and hence become easily heated. This underscores the need for further suppressing temperature rises inside the developing device.